title: Noncovalent enzyme-substrate interactions in the catalytic mechanism of yeast aldose reductase.
abstract: The role of noncovalent interactions in the catalytic mechanism of aldose reductase from the yeast Candida tenuis was determined by steady-state kinetic analysis of the NADH-dependent reduction of various aldehydes, differing in hydrophobicity and the hydrogen bonding capability with the binary enzyme-NADH complex. In a series of aliphatic aldehydes, substrate hydrophobicity contributes up to 13.7 kJ/mol of binding energy. The aldehyde binding site of aldose reductase appears to be 1.4 times more hydrophobic than n-octanol and can accommodate a linear alkyl chain with at least seven methylene groups (approximately 14 A in length). Binding energy resulting from interactions at positions 3-6 of the aldehyde is distributed between increasing the catalytic constant 2.6-fold and decreasing the apparent dissociation constant 59-fold. Hydrogen bonding interactions of the enzyme nucleotide complex with the C-2(R) hydroxyl group of the aldehyde are crucial to transition state binding and contribute up to 17 kJ/mol of binding energy. A comparison of the kinetic data of yeast aldose reductase, a key enzyme in the metabolism of D-xylose, and human aldose reductase, a presumably perfect detoxification catalyst [Grimshaw, C. E. (1992) Biochemistry 31, 10139], clearly reflects these differences in physiological function.
authors.affiliation: Division of Biochemical Engineering, Universität für Bodenkultur (BOKU), Wien, Austria.
authors.forename: W
authors.initials: W
authors.lastname: Neuhauser
authors.forename: D
authors.initials: D
authors.lastname: Haltrich
authors.forename: K D
authors.initials: KD
authors.lastname: Kulbe
authors.forename: B
authors.initials: B
authors.lastname: Nidetzky
mesh_terms: D000449:Aldehyde Reductase / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism; D002175:Candida / Q000201:enzymology*; D005985:Glyceraldehyde / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism; D008658:Inactivation, Metabolic; D010429:Pentoses / Q000378:metabolism; D013045:Species Specificity; D013379:Substrate Specificity; D013780:Tetroses / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D000447:Aldehydes; D006601:Hexoses; D010429:Pentoses; D013780:Tetroses; D005985:Glyceraldehyde; D000449:Aldehyde Reductase; C073321:erythrose